You are assessing a concrete vault that houses a potable water booster pump system. The vault is 2.5 m deep, 2 m wide, and 3 m long, with a single top opening. There is no visible standing water, but it has been sealed for several months. What is the first step you should take before attempting to enter the vault?

Question: You are assessing a concrete vault that houses a potable water booster pump system. The vault is 2.5 m deep, 2 m wide, and 3 m long, with a single top opening. There is no visible standing water, but it has been sealed for several months. What is the first step you should take before attempting to enter the vault?

Answer options:

• Don a full-face respirator with an organic vapour cartridge
• Ventilate the space using a portable blower ✅ Test the atmosphere for oxygen content, flammable gases, and toxic gases
• Contact emergency services to be on standby

Correct answer: Test the atmosphere for oxygen content, flammable gases, and toxic gases

Explanation: Before entering any confined space, it is critical to test the atmosphere for hazardous conditions, including oxygen deficiency/enrichment, combustible gases, and toxic gases. Without this initial test, ventilation or respirator use might be inappropriate or insufficient, and a full assessment of the hazard is not yet made.